Seat Belt Retractor Torque Segmentation for Power Failure Reliability
Solution Overview
Problem
Conventional seat belt retractors rely on electric motors, which fail to function during power outages or motor malfunctions, leading to inadequate user restriction.
Innovation Solution
A retractor system with a spindle wound webbing, a frame, a drawing prevention system, a first torque generating system using a spiral spring, and a second torque generating system using a motor, along with a torque transmitting mechanism that ensures continuous winding torque, even without electric power, and includes a control system for managing torque based on seat belt fastening and collision detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an electric motor is used to wind the webbing, then the winding operation can be automated and controlled, but the system becomes unreliable when power is lost or the motor malfunctions
Solution Approach 1:
The torque generation function is segmented into two independent systems: a first torque generating system (spring-based) that operates continuously without power, and a second torque generating system (motor-based) that provides automated winding when powered. This segmentation ensures that the critical webbing tension function remains reliable even when the automated motor system fails.
Solution Approach 2:
The system changes the operational parameters of the torque generating systems based on power availability. When powered, the motor provides high-speed winding; when unpowered or during emergencies, the spring system provides continuous low-speed torque to maintain webbing tension. This parameter adaptation resolves the contradiction between automation and reliability.
2Power
If a single high-power motor is used for winding, then the winding speed and torque can be maximized, but the system lacks redundancy and fails completely when the motor malfunctions
Solution Approach 1:
The power generation function is divided into two separate torque generating systems with different characteristics. The first system (spring) provides continuous baseline torque without power consumption, while the second system (motor) provides supplemental high-power winding when needed. This segmentation creates functional redundancy that eliminates the single-point-of-failure problem.
Solution Approach 2:
The first torque generating system acts as a cushioning backup that is always ready to maintain webbing tension. It provides a safety margin that compensates for potential motor failures, ensuring that the seat belt restriction function is never compromised even when the primary motor system fails.
3Reliability
If the first torque generating system maintains continuous torque, then webbing tension is always maintained, but the energy consumption increases
Solution Approach 1:
The first torque generating system is a self-contained spring mechanism that generates torque through its own elastic energy storage without requiring external power. It serves itself by automatically maintaining webbing tension through the natural elastic recovery of the spiral spring, eliminating the need for continuous energy input while ensuring reliable webbing tension.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures continuous webbing tension and passenger restriction even in the event of motor failure or power loss, enhancing safety and security.
Implementation Method 1
the first torque generating system generates torque by a rotary spring force of a spiral spring
Data Source
AI summary
A spindle (2) of a seat belt retractor is rotationally driven when required by a motor (5) to the webbing take-up direction side through a power transmission mechanism section (6). Further, the spindle (2) is always connected to a take-up spring (7) and is always subjected to rotational power acting to the webbing take-up side. The structure enables a user wearing a seat belt to be restrained even in failure, realizing a safer and more reliable restraining device.